Extraction of highly polar organophosphorus pesticides from water

Some of the pesticides listed in the European 76/464/EC Directive and in the Directive 2000/60/ EC are very polar and require special analytical methodology with respect to their extraction from water. The extraction of the organophosphorus pesticides methamidophos, omethoate, oxydemeton-methyl, mevinphos and trichlorfon with lg P OW below 1 was investigated using 21 different solid-phase materials. Each material was tested on spiked natural water at 4 different pH values, adjusted prior to extraction. The following range of materials were tested: octadecyl silica, polymers, modified silica, ion exchange and carbon. Extraction of the above compounds from water is possible. A relationship between the octanol-water partition coefficient and recovery rates was obtained not only for octadecyl solid phases but also for some polymeric materials. General conclusions about the use of solid-phase materials and specific conclusions about the extraction of particular compounds were made. An optimized extraction procedure was deduced and confirmed.